netdev - Re: [iproute PATCH v3 0/6] Big C99 style initializer rework

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Date:	Tue, 28 Jun 2016 19:37:23 +0200
From:	Phil Sutter <phil@....cc>
To:	Stephen Hemminger <shemming@...cade.com>
Cc:	Daniel Borkmann <daniel@...earbox.net>,
	David Ahern <dsa@...ulusnetworks.com>,
	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	Julien Floret <julien.floret@...nd.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [iproute PATCH v3 0/6] Big C99 style initializer rework

On Mon, Jun 27, 2016 at 02:10:49PM -0700, Stephen Hemminger wrote:
> On Mon, 27 Jun 2016 20:23:02 +0200
> Phil Sutter <phil@....cc> wrote:
> 
> > Hi,
> > 
> > On Mon, Jun 27, 2016 at 10:59:12AM -0700, Stephen Hemminger wrote:
> > > On Thu, 23 Jun 2016 17:34:08 +0000
> > > Phil Sutter <phil@....cc> wrote:
> > > 
> > > > This is v3 of my C99-style initializer related patch series. The changes
> > > > since v2 are:
> > [...]
> > > 
> > > I like the idea and it makes code cleaner. But doing this introduces lots of warnings
> > > and that is not acceptable.
> > > ip
> > >     CC       ip.o
> > >     CC       ipaddress.o
> > > ipaddress.c: In function ‘print_queuelen’:
> > > ipaddress.c:175:10: warning: missing braces around initializer [-Wmissing-braces]
> > >    struct ifreq ifr = { 0 };
> > >           ^
> > 
> > I saw these too with gcc-3.4.6 but not with 5.3.0. It appears to be a
> > gcc bug[1]. One possible workaround is to match the brace level of the
> > first field, but it's quite ugly: [2]. Another way might be to
> > initialize one of the fields to zero, like so:
> > 
> > | struct ifreq ifr = { .ifr_qlen = 0 };
> > 
> > What do you think?
> > 
> > Thanks, Phil
> > 
> > [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53119
> > [2] http://nwl.cc/cgi-bin/git/gitweb.cgi?p=iproute2.git;a=commitdiff;h=a1cbf2b63c995b2f633c5b4699248ab308b201d2;hp=3809cfec65b03716d1d0360338126df4b4f3fbf6
> 
> I am using gcc on Debian stable which is 5.3.1.

Hmm. In a fresh install of Debian 8.5 I see the warnings as well, but it
has gcc-4.9.2-10 as most recent version.

Another thing I noticed: Using empty braces ('{}') instead of the
universal zero initializer seems to work without causing warnings (at
least unless '-pedantic' is used).

Cheers, Phil